stop_machine: Add stop_core_cpuslocked() for per-core operations
Hardware core level testing features require near simultaneous execution
of WRMSR instructions on all threads of a core to initiate a test.
Provide a customized cut down version of stop_machine_cpuslocked() that
just operates on the threads of a single core.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220506225410.1652287-4-tony.luck@intel.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index cbc3027..0887b3a 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -633,6 +633,27 @@ int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
}
EXPORT_SYMBOL_GPL(stop_machine);
+#ifdef CONFIG_SCHED_SMT
+int stop_core_cpuslocked(unsigned int cpu, cpu_stop_fn_t fn, void *data)
+{
+ const struct cpumask *smt_mask = cpu_smt_mask(cpu);
+
+ struct multi_stop_data msdata = {
+ .fn = fn,
+ .data = data,
+ .num_threads = cpumask_weight(smt_mask),
+ .active_cpus = smt_mask,
+ };
+
+ lockdep_assert_cpus_held();
+
+ /* Set the initial state and stop all online cpus. */
+ set_state(&msdata, MULTI_STOP_PREPARE);
+ return stop_cpus(smt_mask, multi_cpu_stop, &msdata);
+}
+EXPORT_SYMBOL_GPL(stop_core_cpuslocked);
+#endif
+
/**
* stop_machine_from_inactive_cpu - stop_machine() from inactive CPU
* @fn: the function to run
